Technical Abstract:
Species of Cylindrocarpon have a worldwide distribution and are generally considered to be weak or minor pathogens. However, they can sometimes have a significant econimic impact on some hosts especially in synergism with other pathogens. Very little is known about Cylindrocarpon species associated with apple trees in South Africa. Therefore, a survey was conducted in the main apple producting regions of South Africa, which identified four species including C. macrodidymum, C. destructans, C. lirodendri and C. pauciseptatum. Cylindorcarpon macrodidymum was the most prevalent species. Pathogenicity tests on apple seedlings revealed that isolates within each species contained pathogenic isolates that varied in virulence, as well as possible non-pathogenic isolates. The most virulent isolates were identified among some of the C. destructans and C. macrodidymum isolates. A SYBR Green TM real-time PCR method was developed for detection of all four species using Cylindrocarpon genus specific primers on pure culture DNA. High resolution melting analyses of the amplified PCR products allowed differentiation between most of the four species. The real-time PCR method will be evaluated further for its potential to qualify Cylindrocarpon DNA within plant roots collected from the pathgenicity trial, and to determine if a correlation exists between seedling stunting and Cylindrocarpon root DNA concentration.